The present invention relates to a light regulator incorporated in an image pickup system such as a video camera, a still camera, a projector, and a projection system for regulating light upon picking up or projecting an image. The present invention also relates to an image pickup system incorporating the light regulator in a lens barrel.
A light regulator includes a substrate having an optical aperture at an optical path for picking up or projecting an image. At the optical aperture formed in the substrate, one or more blade members are placed. By operating the blade member to open or close, a diameter of the optical aperture is increased or decreased for regulating light. Such a light regulator is widely used due to a relatively simple configuration. For precisely regulating light in multiple levels with such a light regulator, a so-called iris diaphragm is well known. That is, a plurality of blades is arranged uniformly around an optical aperture. In accordance with the number of blades, an aperture diaphragm has a regular-polygon shape such as regular-pentagon and regular-hexagon maintaining a similar shape while a diameter of the aperture diaphragm is changed.
More specifically, around the optical aperture formed in the substrate, a plurality of blades is arranged uniformly such that edges of adjacent two blades are overlapped. The blades are supported at their base end portions by spindles formed on the substrate to freely rotate, and tip portions of the blades face the optical aperture to form the aperture diaphragm. The blade members rotate by a predetermined amount so as to obtain a desired diaphragm diameter.
Such a configuration of the blade member includes two types. One blade type is relatively short in length with acute-angled tip portions, and the blades are overlapped together sequentially to face the optical aperture. The tip portions of the blades are placed inside an aperture edge of the optical aperture to form an aperture diaphragm at most of open/close area. The other blade type is relatively long in length, and tip portions thereof are supported by a substrate around an optical aperture entirely over the open/close area. With the short blade type, every blade is short and small so that their overlapping portion (area) is accordingly small. The drive unit can be thus downsized with lower torque, whereby the system can be advantageously small and compact in size as a whole.
The problem here is that, however, the tip portions of the blades are easily deformed due to their positioning, i.e., the substrate supports only their base end portions, and their tip portions are protruding inside the aperture edge at most of the open/close area. When external forces are applied to the system, the blade tip portions are vibrated so that the light varies in amount. If the blade tip portions are deformed, e.g., warped, blade interference occurs together with light variation, and thus the overlapping blades get stuck with each other, whereby the blades fail to open or close. Such a demerit limits the type of systems such as cameras for use and their use environment, and thus only a limited number of optical devices become applicable.
With the long blade type, the substrate supports the blade tip portions entirely over the open/close area to be ready for backup, and the resulting system can advantageously withstand vibrations occurring thereto and deformation resulted from environmental temperature change. On the other hand, the problem with such long and large blades is that a space occupied thereby is large, and friction among the blades or between the blades and the substrate becomes large. Further, the system is disadvantageously increased in size. In the conventional systems, one of the two different blade types are selected, and the blades are generally configured to be in the same shape.
As described above, when the acute-angled blade tip portions facing the optical aperture form the aperture diaphragm, the blade tip portions configuring the aperture diaphragm may deform. In the configuration, the substrate supports only the blade base end portions, and the deformed blade tip portions cause light variation or a malfunction resulted from the blades getting stuck in each other. To solve such a problem, the blades may be formed large and the blade tip portions may be supported by the substrate around the optical aperture entirely over the open/close area. Such a configuration arises, however, another problem of increasing the system size as described above.
The conventional light regulators have been manufactured with blade configuration and shape appropriate for specifications of cameras or other various optical devices. Accordingly, it is difficult to apply to various optical devices in various environmental conditions.
In view of the problems described above, an object of the present invention is to provide a relatively small light regulator capable of smoothly opening and closing without light variation due to blade deformation, and to provide an image pickup system and a projector using the light regulator. In the present invention, a plurality of blade members configuring an aperture diaphragm at an optical aperture has different shapes to reduce an adverse effect caused by deformation of a blade member or large blade member, thereby preventing blade interference at overlapping portions of the blade members.
Further objects and advantages of the invention will be apparent from the following description of the invention.